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arXiv · 2412.16569

Tunable superconducting diode effect in a topological nano-SQUID

Ella Nikodem·Jakob Schluck·Max Geier·Michal Papaj·Henry F. Legg·Junya Feng·Mahasweta Bagchi·Liang Fu·Yoichi Ando
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Abstract

A Josephson diode passes current with zero resistance in one direction but is resistive in the other direction. While such an effect has been observed in several platforms, a large and tunable Josephson diode effect has been rare. Here we report that a simple device consisting of a topological-insulator (TI) nanowire side-contacted by superconductors to form a lateral Josephson junction presents a large diode effect with the efficiency $\eta$ reaching 0.3 when a parallel magnetic field $B_{||}$ is applied. Interestingly, the sign and the magnitude of $\eta$ is tunable not only by $B_{||}$ but also by the back-gate voltage. This diode effect can be understood by modeling the system as a nano-SQUID, in which the top and bottom surfaces of the TI nanowire each form a line junction and $B_{||}$ creates a magnetic flux to thread the SQUID loop. This model further shows that the observed diode effect marks the emergence of topological superconductivity in TI-nanowire-based Josephson junction.

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Ella Nikodem, Jakob Schluck, Max Geier, Michal Papaj, Henry F. Legg, Junya Feng, Mahasweta Bagchi, Liang Fu, Yoichi Ando. 2024-12-21. Tunable superconducting diode effect in a topological nano-SQUID. https://arxiv.org/abs/2412.16569

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